Article handling equipment known as palletizers are well known in the art. Palletizers receive randomly oriented articles, such as for example beverage containers in bulk onto a pattern forming area; form said articles into a patterned group or layer usually having adjacent longitudinal rows staggered with respect to each other to achieve an efficient packing factor; and sweep successively formed layers in succession onto a pallet positioned further downstream on a hoist. After each layer is swept from the pattern forming area onto the pallet, a separator sheet such as chipboard is placed over the layer, and the hoist is lowered incrementally to a position for receiving the next subsequent layer on top of the separator sheet. The cycle of pattern forming, sweeping onto the pallet, separator sheet placement, and pallet lowering is carried out until the pallet is loaded to include a preselected number of layers.
In one prior art type device, randomly supplied articles accumulate on a conveyor driven accumulator area, the output of which is gated by raising and lowering a set of holding pins. Articles are gated from said accumulation area into a carriage, which comprises a generally rectangular frame member mounted on longitudinally extending rods. The carriage moves back and forth in a cyclical fashion for transporting patterned layers or groups one at a time to a pallet. The carriage frame has a pattern former fixedly attached to a front retaining cross member, the pattern former being formed from a plurality of vertically extending pins welded to the pattern former, with alternate ones of said pins being offset from one another transversely for forming pockets that stagger the front transverse row of articles as articles are admitted thereto and urged thereagainst by line pressure. When a full group is in said carriage, a set of carriage pins mounted towards the rear of the carriage descends to engage and separate the group, as the carriage moves downstream to sweep the layer from the pattern forming area onto the pallet. After the sweeping operation the carriage moves back to its initial position and, when so repositioned, the holding pins and carriage pins are raised to allow the next subsequent group of articles to enter. Because the carriage must return to its initial position before admitting the next group, time is thereby consumed in a nonproductive manner because the flow of articles from the accumulation area to the pallet is disrupted for a significant time interval each cycle in waiting for the carriage to return to its initial position.
Other palletizers in the art are known for providing a more continuous flow of articles. U.S. Pat. No. 3,934,713 to Van der Meer et al. discloses a conveyor 42, sweep assembly 46, and passage inhibiting assembly 50 which cooperate to begin the conveyance of a second group of containers from receiving station 52 to sweep station 48 while the sweep assembly is positioning itself for a new group, whereby the overall time required for receiving containers and transferring layers thereof to pallet 14 is reduced. However, this device has the disadvantage that timing is particularly critical, as the sweep moves to push articles onto the pallet and articles are received on a pattern former behind the sweep attached to a common endless chain. If proper chain timing is not achieved, articles being transferred onto the pallet may be tipped over, while articles moving in behind may impact the pattern former in an unstable manner.
Other palletizers are shown for example in U.S. Pat. No. 3,389,6,810 to Wolfe et al. and U.S. States Pat. No. 3,027,020 to McCoy.